Starch Degradation in Synchronously Grown Chlamydomonas reinhardtii and Characterization of the Amylase

Abstract

The activities of amylase and phosphorylase were monitored during the 12-hour light/dark synchronous cell cycle of autotrophically grown Chlamydomonas reinhardtii 11-32/90. The activity of amylase increased from 7.3 to 42 micromole reducing equivalents per 10(9) cells per hour while phosphorylase increased from 43 to 214 micromole glucose 1-phosphate released per 10(9) cells per hour between the midlight and middark periods. Cellular fractionation indicated that both enzymes were localized solely within the chloroplast. The pH optima for amylase and phosphorylase were 6.7 to 7.6 and 6.0 to 7.4, respectively. The amylase is a heat-labile alpha-amylase which is insensitive to ethylenetetraaecetate but inhibited by N-ethylmaleimide.